how to mend it - Fix appliances, electricals, gadgets, cars... Ask for free help
:: home
:: add a question
:: search
:: help
:: most recent
:: unanswered
   Search: Go 
Fixed for free!
Ask Your Question
Popular

These categories may also be of interest ...

Bathroom Appliances, Electric Toothbrushes

Bathroom Appliances, Hair Straighteners

Bathroom Appliances, Hairdryers

Bathroom Appliances, Shavers

Full list

... mend, fix, or repair just about anything.

Help someone
  Are you good at fixing things?  

Click here to help

Fault info.
Click here for Kia repair information.
First time?

howtomendit.com costs nothing to use and you can ask a question without an account or logging in.

Click here to ask a question.

Answers

Who answers the questions?

Other users of howtomendit.com provide the answers. The more detail and information you provide in your question the easier it is for others to help you.

Search for a fix
How can I fix my
Baths and Shower?
Mend it
How can I repair my Potterton Netaheat?
Categories > Mend Bathroom Appliances, Baths and Showers > Question
Q & As - mend, repair, fix bathroom appliances, baths and showers, drip, water, hot, cold, pressure, water pressure, jet, shower head, power shower, electric showerNavigate to ...
Bathroom Appliances, Baths and Showers (4797 other questions)
Other categories
Add a question



Mend > Baths and Showers

Question - mend, repair, fix

Water hammer?

When toilet flushed really noisey banging but if i run cold water it stops so what do I need to do to get rid of it.



Pug106
May 2018

To add an answer, click here To add a new question, click here To find all other questions, click here

Answers - mend, repair, fix

Water hammer is usually caused by the rapid shut-off of water which is flowing in pipework. Water is heavy and builds up momentum as it travels and suddenly stopping the flow causes the moving water to 'pile up' at the obstruction (valve) causing a local sharp pressure spike. As the moving water slows to a stop, the high-pressure region at the closed valve now bounces back up the water in the pipe, traveling considerable distances throughout the house pipework as a pressure wave. It can bounce back and forth several times before finally decaying and this is why you can hear it in many places within the property, not just at the origin, and the pipes can often move about as if someone was hitting them. It's worse in rigid pipework (copper) and can be caused by quarter-turn ceramic insert taps being closed too quickly, washing machine solenoid valves, but most commonly by old style (BS1212 Part 2 &3) direct-acting float valves in either toilet cisterns or in storage cisterns in the loft/attic. Even modern equilibrium float valves (BS1212 Part 4) can cause water hammer in certain unfavourable circumstances.

If you have water hammer, first check for any float valves you have in the house. Work out when it happens - if it's after you flush, check the WC valve. If it's after you draw off hot water (or cold water in the bathroom) check the attic for a cold water storage cistern. If the valve is old, and the water supply has a decent pressure (more than 1 bar) and is clean (no regular grit or other debris) then replace the valve with a modern BS1212 Part 4 equilibrium valve (e.g. Fluidmaster, Torbeck). Check that the discharge gap between the valve outlet and the final water level in the cistern isn't too large (must be at least 20mm by regulation, for 15mm pipework) since too great a gap can cause waves during filling, which tend to oscillate the valve's float, inducing continuous water hammer as the cistern approaches full and the valve begins to close.

If it happens after the washing machine stops filling, try replacing the machine's cold water inlet hose for a new one (they're cheap) since they are intended to absorb some of the pressure spike that occurs whenever the fast-closing solenoid inlet valve shuts off. If that doesn't fix it, you can install a 'mini expansion vessel/arrestor' close to the end of the pipework supplying the washing machine. If you do so, make sure it's the proper WRAS approved type, suitable for drinking water (it should be blue or silver, and not red which is only for central heating).

You can also easily check your cold water supply pressure, since the test gauges are cheap these days. If it is over 3bar, you might well consider fitting a decent pressure reducing valve to the incoming supply, and reduce your supply pressure to 2-3bar which will will be much kinder to your valves and fittings and will help reduce the risk of water hammer. Avoid the cheapest ones since the performance will be correspondingly poor - the Honeywell one (black stem, green knob) works well.

Finally, be thorough in your investigation. In an old property I worked on, all the ball valves were of a similar vintage and they all had an interaction with each other. When I replaced one noisy one, immediately another one (on the same pipework but upstairs) started to hammer, and turned out to be the actual culprit which was inducing the first one to hammer by means of a travelling pressure spike! So in this scenario, don't give up if you don't fix it first time.

Sparks (the Plumber)
May 2018

I think you need to change the float valve. It may be opening and closing rapidly when the toilet is filling.

Try watching the inside of the cistern whilst flushing. Try forcing the float mechanism down with your hand and see if it hammers when it isn't controlling the flow.

Gary
May 2018

To add an answer, click here    

Add An Answer Form

Add your answer using the form below ...

The question: Water hammer?
Your answer:

(Add your answer here. Try to include as much detail as possible.)
Your name:

(Enter your name as you wish it to be displayed.)
Other questions in this category - Bathroom Appliances, Baths and Showers
Do I have to turn off water to replace aquastream cartridge?

Do I have to turn off water to change aqualise aquastream cartridge...

Click here for the fix.
How can I fix my shower.Sceptre universal thermostatic mixer shower?

My shower is running cold and my hand control set is stuckl The unit is 811146 Sceptre Universal Thermostatic mixer shower...

Click here for the repair.
where is the reset button on my Mira Advance thermostatic shower ?

The shower is bleeping and flashing reset button...

Click here for the repair.
i have a aqualisa shower bur will not turn on?

aqualisa shower will not turn on...

Click here for the fix.
mira excel shower - does not turn off completely?

mira shower - probably 20 years old - unable to turn off completely - is there a replacement washer and if so, is it easy to change....

Click here for how to mend it.
Mira 8 drip?

How to stop Mira 8 shower from dripping after service kit fitted....

Click here for how to mend it.
replace cord in ceiling mounted fan isolator switch for extractor.?

The cord broke when fan is on, so the OFF indicator is inside the housing. Looks a bit like BG 10A fan Isolator ceiling switchin pictures. I took it off the ceiling, theres a broken elastic band in there dont know its function....had a go but its not working....

Click here for how to mend it.
Leaking at the back of hose.?

Where the hose connects to the shower water is coming out at the back of it....

Click here for how to mend it.
Fix what?
Telephones, Cordless Phone - fix/mend/repair/service information
Household Appliances, Tumble Dryers - fix/mend/repair/service information
Video, HD Televisions - fix/mend/repair/service information
Help wanted!
Advertisements
Fixed!
Can't believe the method worked, but it really did! Thank you.

Rachel
Dec 2019


Mend it
How can I correct an engine missfire?
All appliances!

To mend any household, kitchen, or other electrical appliance start here.

To search for repair advice click here.

To find out how to mend it click here.

Mend it
How can I repair my Chevy?
Fault find
Click here to fix Mountfield products.
Advertisements
Important

Attempting repairs can be dangerous.
In many instances work should only be undertaken by a qualified professional.
Ensure you have read our Small Print page before using information supplied via this website.

©  2003 vE
We use Cookies. See our Privacy Policy.